Immunoassays are particularly useful for their speed and specificity. Immunoassays make use of the specificity of antibodies and/or immunoglobulins to particular molecules. Recent technology has allowed immunoassays to be miniaturized and compartmentalized so as to be usable as test strips by easily used unskilled or non-healthcare workers to diagnose diseases, medical conditions and/or the presence of metabolites. Traditional test strips use techniques of chromatography to separate components as a solvent front moves upward through a substrate. However such “paper” chromatography provides separation of components in a sample does not provide specificity in identifying those components.
More recently, test strips have been designed to use the forces of capillary action to move the solvent front laterally, across the length of a test strip. Such “lateral flow” test strips increase the ease of use of such strips and by utilizing lateral flow are able to provide a platform for holding the assay components, in micromolar quantities dried along the length of the substrate to provide specific identification of molecules in a sample. Because of their ease of use and reliability lateral flow test strips are widely used in the field and by non-laboratory personnel to provide reliable data on the presence of drugs, chemicals and metabolites in a sample. A widely spread and well known application is the home pregnancy test.
Lateral flow assays make use of the force of capillary action to draw a solvent, in a lateral fashion through capillary beds formed in or on a substrate through a series of active regions on the test strip to provide a complete immuno assay reaction and provide a recognizable result at the other end of the test strip by the time the solvent/reaction has reached the end of the strip.
The typical test strip includes a series of active regions or elements that provide various components of the assay. Generally, the first element or portion includes a sample pad which acts as a sponge and holds an excess of sample fluid (such as urine, blood, plasma or saliva). Once the sample pad is wetted by the sample the fluid migrates to the second element or portion (conjugate pad) on which has been immobilized various reagents and/or bioactive particles needed to carry out the immunoassay, such reagents and/or bioactive particles include salts and or sugars to provide a proper pH, antibodies to a specific antigen, or antigens to a specific antibody. As the solvent front moves along the flow path, it dissolves the immobilized reagents and brings them in contact with particular proteins and/or molecules in the sample. The solvent front then carrying the immunoreaction then moves to a third area, often referred to as the stripes where a third molecule binds to the antibody/antigen complex. This third molecule is often a visual signal such that the reaction changes color upon reaching the stripes. Oftentimes the third area includes at least two stripes. One denoting a positive reaction and a second denoting a negative reaction. In some cases, there may be a positive control stripe (signifying that the reaction worked as intended), a negative control stripe (indicating that the reaction did not work and should be redone), a positive outcome stripe and a negative outcome stripe. Beyond the stripe region there is typically a further absorbent material which acts as a wick to remove and absorb any remaining fluid.
While current lateral flow assays have proven extremely useful and reliable, the suffer in their ability to support more sophisticated assays requiring increased incubations times, positive and/or negative controls and consequent reliability in results and field use and variation in molecules the assays are useful for.
Numerous systems and instruments have been created to aid in the detection of illegal drugs or compounds in persons suspected of imbibing, ingesting, injecting, or inhaling illegal or controlled drugs or compounds. These systems have been created for use in the fields of law enforcement, employment screening, and emergency medical treatment. These systems range from handheld portable single use devices to specimen containers that are analyzed with laboratory equipment. There is a need for single use disposable test devices that can be used for the analysis of more than one target compound, that can be visually read and also readable by electronic readers, and that provide enhanced accuracy, ease of use and low cost.
Known lateral flow assay test devices suitable for field use do not have the accuracy and low point detection that laboratory equipment provides. One reason for this is that the laboratory setting allows for the technician to perform multiple steps and extend and precisely time incubation and sample conditioning times. Such is not conducive to field use and use by untrained personnel. It would be very advantageous of some of the functionalities of the laboratory setting could be adapted to field use by untrained personnel thus providing enhanced accuracy and low point detection, particularly of drugs of abuse.
Moreover, existing disposable single use devices lack flexibility in activating the test processes. The test process starts when the sample is received in the lateral flow assay test device. Delaying the start of the test processing could be very useful, such as where a sample or group of samples are taken and the test giver wishes to delay the device processing and the reading. For example, it would be expedient to provide tests to groups of individuals serially and delay the activation of the test device process until the group has been tested. Such would save considerable time for each of the test subjects and be more efficient for the test administrators. Current disposable devices do not readily have such capability. Such devices need to be easily visually readable and inexpensive.
Moreover, such devices should be able to be manufactured utilizing known high speed manufacturing techniques such as described in U.S. Pat. Pubs. 2012/0061010 and 2007/0040567; U.S. Pat. No. 8,119,414;